Plastic Corrugated Container with Ultrasonically Formed Score Lines

ABSTRACT

A corrugated plastic box and a method for manufacturing a corrugated plastic box from a blank are provided. The method includes the steps of forming rounded edge seals on the perimeter edges of the blank, pre-sealing portions of the blank to form a plurality of areas in which major and minor flap slots and a glue tab are desired, ultrasonically scoring the blank to form a plurality of flap score lines, and cutting the blank through the plurality of pre-sealed flap slots and glue tab, leaving a sealed edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 61/920,570 filed Dec. 24, 2013, the contents of whichare incorporated herein by reference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

N/A

TECHNICAL FIELD

The present invention generally relates to a reusable plastic corrugatedcontainer or more specifically box with smooth outer edges and sealedflap slots, and ultrasonically formed score lines, and to a process formanufacturing reusable plastic corrugated containers and boxes withsmooth sealed outer edges and sealed flap slots, and having flap scorelines that allow these containers and boxes to be used and reused inconventional paper corrugated packaging automation lines which mayinclude case erectors, case packers, box closure and sealing systems,and palletizers.

BACKGROUND OF THE INVENTION

Corrugated plastic relates to extruded double-walled plastic-sheets, orliners, produced from polypropylene or polyethylene resin. Corrugatedplastic sheets have a generally similar construction to corrugatedpaperboard. There are two layers of sheets or skins connected by flutesdisposed and connected therebetween to form the corrugated sheet. Onetype of corrugated plastic material is known as “plastic profile board.”As opposed to the flutes being undulating waves, as they are inpaperboard corrugation and certain other plastic corrugated materials,the flutes in a plastic profile board are typically more like ribs andthe profile is preferably extruded.

The plastic corrugated sheets can be transparent to allow lighttransmission, or they can be custom colored or translucent to signify anowner or manufacturer, or to block the transmission of light. The spacebetween the outer skins act as an insulator. Graphics can also beapplied to the outer surfaces and inner surfaces of the outer layers.

Chemically, corrugated plastic sheets are inert, with a neutral pHfactor. At regular temperatures most oils, solvents and water have noeffect, allowing the corriboard to perform under adverse weatherconditions or as a product component exposed to harsh chemicals.Standard corrugated plastic sheets can be modified with additives, whichare melt-blended into the sheet to meet specific needs of the end-user.Special products that require additives can include: ultra-violetprotection, anti-static, flame retardant, custom colors, corrosiveinhibitors, static-dissipative, among others.

The Wiley Encyclopedia in Packaging Technology (“Boxes, Corrugated” inThe Wiley Encyclopedia of Packaging Technology, eds. Brody A and MarshK, 2nd ed, John Wiley & Sons, New York) identifies the followingstandard flute designations used in the United States for paperboardcorrugations:

Flutes per Flute Flutes per Flute Flute linear thickness linearthickness Designation foot (in) meter (mm) A flute 33 +/− 3 3/16 108 +/−10 4.8 B flute 47 +/− 3 ⅛ 154 +/− 10 3.2 C flute 39 +/− 3 5/32 128 +/−10 4.0 E flute 90 +/− 4 1/16 295 +/− 13 1.6 F flute 128 +/− 4  1/32 420+/− 13 0.8

Corrugated plastic can be used to form boxes and other similarcontainers. A variety of equipment has been used to convert paper andplastic corrugated material into boxes. The equipment is selected basedon production run size, box size, and box quality in terms of tolerancesand aesthetic appearance. This equipment includes flexographic, silkscreen and digital printing machines; quick set, rotary, clam shell orflatbed die cut machines; and manual, ultrasonic welding, and automatedfolding and gluing machines for assembly.

Paper corrugated boxes are often used only once and then discarded.After a paper corrugated blank is converted into a box and used, itcannot typically be re-used in automated packaging lines designed towork with new, straight and flat boxes. This is in part because themajor and minor flaps of a paper corrugated box will not return to theiroriginal vertical alignment after use, and in part because the creasesand scores of a paper corrugated box lose integrity with each use. Insuch instances, the flaps become floppy or limp. Additionally, paperboxes cannot be washed or otherwise cleaned, and therefore cannot bereused in instances where sanitation is important (e.g., food items,etc.)

Therefore, the industry has long sought a re-usable container (i.e., onethat can be cleaned or sanitized and then re-used), and has attempted tomake a re-usable plastic corrugated container. As with paper corrugatedcontainers, it is desirable that plastic corrugated containers are ableto be used with conventional paper converting equipment (e.g., equipmentthat folds a cut/scored blank of material into a box). Previous methodsto convert plastic corrugated material into boxes have used conventionalpaper corrugated converting equipment and process flow. This processflow includes making plastic corrugated material blanks to theappropriate size and then die cutting the blank using quick set, rotary,clam shell or flatbed die cutting machines. The die cut blanks are thenassembled by bonding a glue tab and one of the panels to form a box. Theblank may also be printed upon.

A lingering problem with current attempts to create a re-usable plasticcorrugated container is that it must be able to return (after being usedin a box form) to a flat state with the flaps aligned or coplanar withthe side wall panels of the blank in order to be refolded in the boxconverting equipment. Industry efforts to this point have failed toprovide such a container. In particular, the fold or score linesconnecting the upper or lower flaps or panels to the side panels of thebox must be able to bend (i.e., during a box forming process), and alsohave sufficient memory to revert to a straight position (i.e., coplanaror aligned with the box side panel) to again be reformed into a box(after sanitizing) using the converting equipment. However, the scorelines cannot be made with too much memory so that after use, they havetoo much bounce-back or spring-back making them difficult for theconverting equipment.

In addition, it is desirable to seal the edges to prevent intrusion ofwater, bacteria, or other debris, bugs or contaminants into the flutedarea. This is particularly important for containers used with food andpharmaceutical products. Previous methods for sealing the edges ofplastic corrugated material boxes have used either clam shell or flatbeddie cutting machines during the converting process. The seal is formedin the die cut process using heat and pressure to pinch and weldtogether the inner and outer surfaces of the plastic corrugated materialalong the edge. This forms a sealed, but sharp edge, which is notacceptably ergonomically safe in most applications. Some limited successhas been found using these processes for lighter densities of plasticcorrugated material. While the process still leaves a sharp edge, thelighter densities make edge sealing acceptable for limited useapplications, but not multiple re-use applications.

In addition to the above problems, it is also desirable to reduce thenumber of steps needed to create and process plastic corrugated boxesand to increase the processing speed. Due to environmental concerns, itis anticipated that many companies will insist on or otherwise turn tore-usable containers in the near future. Thus, the demand for suchcontainers will rise and the speed of the plastic container processingwill become a more pressing issue.

Assignee of the present development, Orbis Corporation has beendeveloping and refining plastic corrugated containers and the processesfor forming them. Examples of recent Orbis Corporation developments aredescribed in U.S. patent application Ser. No. 14/265,977, filed Apr. 30,2014, titled “Plastic Corrugated Container with Sealed Edges” (AttorneyDocket 52045-7485), U.S. patent application Ser. No. 14/265,935, filedApr. 30, 2014, titled “Plastic Corrugated Container with Manufacturer'sJoint Adding Zero Extra Thickness” (Attorney Docket 52045-7484), U.S.patent application Ser. No. 13/273,019, filed Oct. 13, 2011, titled“Plastic Corrugated Container with Improved Fold Lines and Method andApparatus for Making Same,” (Attorney Docket 52045-7426), U.S. PatentApplication No. 61/920,570, filed Dec. 24, 2013, titled “PlasticCorrugated Manufacturing Process” (Attorney Docket 52045-7461), and U.S.Patent Application 62/062,481, filed Oct. 10, 2014, titled “PlasticCorrugation” (Attorney Docket 52045-6509), all of which are incorporatedherein by reference.

Aspects of the present invention are applicable for a variety ofcontainer and box types. The most common box style is a regular slottedcontainer (RSC) having four side panels with four top flaps (for forminga top) and four bottom flaps (for forming a bottom). For a rectangularshaped box, the two longer flaps are referred to as the major flaps andthe two shorter flaps as the minor flaps. Another common box style is ahalf slotted container (HSC). The HSC is similar to the RSC except thatit only includes the bottom set of flaps and has an open top. In theHSC, the top edge of the blank used to form the box becomes the upperedge of the box side panels. Other types of boxes (e.g., autolock, autoerect or crash lock boxes-ALB) can also be formed using various aspectsof the invention as well.

The present invention is provided as an improved plastic corrugatedcontainer and process for forming the container.

SUMMARY OF THE INVENTION

The present invention provides an improved plastic corrugated boxmanufacturing process resulting in a plastic corrugated box with saferounded sealed edges on the edges most frequently contacted by humanhands. Sealing is desirable, particularly in certain applications suchas transport and storage of food items. Sealing prevents food, insects,water, or other contaminants or debris from entering the interstices ofthe flutes in the corrugated material, and bacteria or mold from growingtherein.

The process of the present invention also allows for the creation of amanufacturer's joint (the connection between one end of a blank with theother end when forming the blank into a box shape) that reduces theamount of bowing in a stack of blanks. Preferably, the manufacturer'sjoint adds no additional thickness to each blank. The process alsoallows for major and minor flap score lines that allow the plasticcorrugated material boxes to return to an original straight position foruse in conventional automated packaging lines. The process of thepresent invention also provides a plastic corrugated blank that can beconverted into a box using conventional paper corrugated convertingequipment.

The process confers a number of advantages over the prior art. Forexample, the resulting edge seals and score lines can be performed in amore controlled and, therefore, consistent process. This results in amore robust plastic corrugated box. Additionally, the plastic corrugatedboxes prepared in this manner can be die cut and assembled onconventional paper corrugated converting equipment, including rotary diecutters, and can be processed at higher speeds. Also, the plasticcorrugated boxes are able to return to their original shape as the scorelines formed by the present invention will have “memory” that returnmajor and minor flaps to straight after each use.

In one embodiment, the present invention provides a method formanufacturing a corrugated plastic blank that includes the steps offorming rounded edge seals on the perimeter edges of the blank,pre-sealing portions of the blank to form a plurality of areas in whichmajor and minor flap slots, a glue tab, and a fourth side wall paneledge are desired, scoring the blank to form a plurality of flap hinges,and cutting the blank through the plurality of pre-sealed flap slots,glue tab and fourth side wall panel areas, leaving a sealed edge. Thescoring is preferably performed by rotary ultrasonic reshaping of thecorrugated structure in the score line.

The blank includes fold and/or score lines defining a pair of opposingside wall panels and a pair of opposing end wall panels. The blank alsoincludes bottom and possibly top flaps extending from the pair ofopposing side walls, and bottom and possibly top flaps extending fromthe pair of opposing end walls. The blank further includes rounded sealsalong the perimeter edges of the blank, and a plurality of flap slotssealed along their edges.

In accordance with one embodiment of the invention, a plastic corrugatedbox which can be reused in box converting machinery is disclosed. Theplastic corrugated box comprises at least a first side wall panel havinga top portion and a bottom portion and a first bottom flap connected tothe bottom portion of the first side wall panel by a firstultrasonically formed score line. It has been found that ultrasonicallyforming the score line of a plastic corrugated box reshapes thestructure of the plastic in that area. The reshaped structure allows forfolding the flap about the score line when forming a box, and providessufficient memory to return the flap to a straight position (i.e.,coplanar or aligned with the plane of the side wall panel) after use.This enables the corrugated box to be collapsed and then (along with astack of other similar boxes) reformed into a box in a box convertingapparatus. Such apparatuses require the flaps to be straight andcoplanar or aligned with the side wall panels.

The first bottom flap can be formed to include a smooth sealed loweredge. For a Half Slotted Container box style, the first side wall panelcan be formed to include a smooth sealed upper edge.

The plastic corrugated box can further comprise a second side wall panelhaving a top portion and a bottom portion connected to the first sidewall panel by a first fold line, a third side wall panel having a topportion and a bottom portion connected to the second side wall panel bya second fold line and a fourth side wall panel having a top portion anda bottom portion connected to the third side wall panel by a third foldline and to the first side wall panel by a manufacturer's joint.Similarly, the box can include a second bottom flap connected to thebottom portion of the second side wall panel by a second ultrasonicallyformed score line, a third bottom flap connected to the bottom portionof the third side wall panel by a third ultrasonically formed score lineand a fourth bottom flap connected to the bottom portion of the fourthside wall panel by a fourth ultrasonically formed score line.

Again, for the Half Slotted Container style box, all of the bottom flapscan include a smooth sealed lower edge, and all of the side wall panelscan include a smooth sealed upper edge.

For a Regular Slotted Container box style (and certain other box styleshaving top flaps), the box can include a first top flap connected to thetop portion of the first side wall panel by a fifth ultrasonicallyformed score line, as well as a second top flap connected to the topportion of the second side wall panel by a sixth ultrasonically formedscore line, a third top flap connected to the top portion of the thirdside wall panel by a seventh ultrasonically formed score line and afourth top flap connected to the top portion of the fourth side wallpanel by an eighth ultrasonically formed score line. Each of the topflaps can include a smooth sealed upper edge.

The ultrasonically formed score lines do not have to extend across afull width of the flap and/or corresponding side wall panel. Instead,the ultrasonically formed score line can comprise a plurality of spacedapart ultrasonically formed segments across a width of the flap and/orcorresponding side wall panel.

In accordance with another aspect of the present invention, a plasticcorrugated blank for forming a box is disclosed having a generallyrectangular portion of plastic corrugated material. The blank includes aplurality of fold lines forming side edges of a plurality of side wallpanels. The plastic corrugated material can have a first plurality ofultrasonically formed score lines where each score line of the firstplurality of ultrasonically formed score lines forms an edge between oneof the plurality of side wall panels and a bottom flap connected to theone side wall panel. Similarly, the plastic corrugated material can havea second plurality of ultrasonically formed score lines where each scoreline of the second plurality of ultrasonically formed score lines formsan edge between one of the plurality of side wall panels and a top flapconnected to the one side wall panel. The blank can have a smooth sealedtop edge and a smooth sealed bottom edge.

In accordance with another aspect of the present invention, a processfor forming a re-useable plastic corrugated box is provided. The processcomprises providing a sheet of plastic corrugated material having a topedge and a bottom edge and ultrasonically forming a first score line inthe sheet of plastic corrugated material using an ultrasonic device.

The process can further include forming a plurality of fold lines in thesheet of plastic corrugated material where the fold lines define aplurality of side wall panels of the box and the first score linedefines a bottom flap for one of the plurality of side wall panels.Additionally, the step of ultrasonically forming a first plurality ofscore lines in the sheet of plastic material can be performed where eachof the first plurality of score lines define a bottom flap for acorresponding side wall panel.

The process can further comprise ultrasonically forming a second scoreline in the sheet of plastic corrugated material where the second scoreline defines a top flap for the one of the plurality of side wallpanels, or ultrasonically forming a second plurality of score lines inthe sheet of plastic material where each of the second plurality ofscore lines define a top flap for a corresponding side wall panel.

The process can further include forming a smooth sealed top edge of thesheet and forming a smooth sealed bottom edge of the sheet. The processcan also include cutting slots between the bottom flaps and the topflaps, forming a glue tab at a first end of the sheet of corrugatedmaterial and, connecting the glue tab to a second opposing end of thesheet of corrugated material. Additionally, the process can includeproviding automated box converting equipment for opening and folding thesheet of plastic corrugated material.

The step of ultrasonically forming the score lines in the sheet ofplastic corrugated material can comprise contacting a first surface ofthe sheet with an anvil of a rotary ultrasonic device. The anvil can beprovided with a first projection on a contacting surface of the anvil.Additionally, this step can include contacting a second surface of thesheet opposing the first surface with a horn of the rotary ultrasonicdevice. The horn is provided to supply the ultrasonic energy. However,either the horn or the anvil can be configured to supply the ultrasonicenergy to the sheet. Alternatively, other ultrasonic devices could alsobe used.

The ultrasonically formed score line can be continuous throughout eachflap. Alternatively, each ultrasonic score line can be formed byultrasonically reshaping a plurality of spaced apart linear segments inthe sheet.

In accordance with yet another embodiment of the invention, a processfor forming a plastic corrugated box is provided that comprisesproviding a generally rectangular sheet of plastic corrugated materialhaving a first outer layer, a second outer layer and a plurality offlutes extending in a first direction between the first and second outerlayers. The process further comprises forming a plurality of fold lineson the sheet in the first direction where the fold lines define aplurality of side panels of the box and ultrasonically forming a firstplurality of score lines on the sheet in a second directionperpendicular to the first direction where the first plurality of scorelines defining a plurality of bottom flaps extending from a bottomportion of the side panels. The process can further includeultrasonically forming a second plurality of score lines on the sheet inthe second direction where the second plurality of score lines define aplurality of top flaps extending from a top portion of the side panels.The process further includes cutting a plurality of slots between thebottom flaps and cutting a plurality of slots between the top flaps. Thecutting step can be performed in a die cutting machine.

Again, the ultrasonic forming of the score line can be performed with arotary ultrasonic device having a horn and an anvil, or other ultrasonicdevices.

The process can further include forming a glue tab at a first end of theplastic sheet and connecting the glue tab to a second end of the plasticsheet. The process can use box converting equipment by placing theplastic sheet in a box converting apparatus, opening the box using theapparatus and folding the bottom flaps using the apparatus.

One unique aspect of the invention involves pre-sealing portions of thecorrugated plastic material in certain areas of the blank prior toperforming other operations. As used herein, “pre-sealing” (or“pre-sealed”) refers to crushing and/or welding or ironing the plasticso that it will no longer have memory to later revert to its originalshape. This can include sufficiently melting some or all of the materialin the area being pre-sealed. In effect, the pre-sealing bonds the twoouter skins and intervening flutes of the material together so that thepre-sealed area maintains a permanently flattened state. Pre-sealingallows for forming a manufacturer's joint that does not (upon formationor later) increase the thickness of the blank. It also enables portionsof the blank to be die cut more easily (e.g., for the flap slots) usingconventional die cutting apparatuses, and with better results.

In accordance with yet another embodiment of the invention, a processfor forming a plastic corrugated box having a plurality of side wallpanels comprises providing a sheet of plastic corrugated material,forming a plurality of fold lines in the sheet where the fold linesdefine a plurality of side wall panels, forming a plurality of scorelines in the sheet where the score lines define a plurality of flapsextending from the side wall panels, and pre-sealing a plurality ofsegments on the sheet at positions for forming a plurality of slotsbetween the flaps. This pre-sealing step is performed prior to cuttingslots between the flaps.

The process can further include pre-sealing at least a first portion ofa first end of the sheet and at least a first portion of a second end ofthe sheet. These pre-sealed end portions can be used for formation of amanufacturer's joint (the connection of one end of the blank to theother end when forming a box).

The process can further include forming a smooth sealed top edge of thesheet and forming a smooth sealed bottom edge of the sheet. The smoothsealed edges can be formed using heated dies. The dies can be curved orarcuate, flat or some other smooth shape.

The process further includes cutting slots within the plurality ofpre-sealed segments. This can be done by placing the sheet in a diecutting apparatus. The die cutting apparatus can also be used forcutting a second portion of the first end of the sheet to form acentrally located pre-sealing glue tab.

The step of pre-sealing a plurality of segments on the sheet atpositions for forming a plurality of slots between the flaps cancomprise applying heat and pressure to the sheet at the segmentpositions. Alternatively, this step can comprise ultrasonically weldingthe sheet at the segment positions. The ultrasonic welding can beperformed by a plunge ultrasonic device or by a rotary ultrasonicdevice. If a rotary ultrasonic device is used the process can includethe steps of contacting a rotatable anvil of the rotary ultrasonicdevice on a first outer surface of the sheet at the segment positions,and contacting a rotatable horn of the rotary ultrasonic device on asecond outer surface of the sheet where the horn is aligned or inregistration with the anvil.

Additionally, the process can include forming air escape holes in thesheet proximate the segment positions. This allows air trapped in theflutes between the outer sheets of the plastic corrugated material toescape during the pre-sealing step. Otherwise, random air holes (causedby trapped air) can form in the blank during this process and squeezeout of molten plastic (during pre-sealing) can extend beyond the blankedge.

Another issue that can occur during the pre-sealing process is lumpsfrom excess plastic in the pre-sealed flattened areas. Accordingly, theprocess can include directing the excess plastic of the sheet formedwhen pre-sealing the segments into desired locations. One method ofdirecting the excess plastic is providing the anvil (when using a rotaryultrasonic device, or the contacting surface of other types ofultrasonic devices) with a contacting surface having peaks and valleys.The valleys provide a location for the excess plastic to move to duringthe pre-sealing step. Preferably, the process includes providing anundulating wave pattern of raised ridges on the contacting surface.

In accordance with another embodiment of the present invention, aprocess for forming a plastic corrugated box comprises providing agenerally rectangular sheet of plastic corrugated material having afirst outer layer, a second outer layer and a plurality of flutesextending in a first direction between the first and second outerlayers, forming a plurality of fold lines on the sheet in the firstdirection where the fold lines define a plurality of side panels of thebox and forming a plurality of score lines on the sheet in a seconddirection perpendicular to the first direction where the plurality ofscore lines define a plurality of flaps extending from the side panels,and pre-sealing a plurality of segments on the sheet at positions forforming a plurality of slots between the flaps. The step of pre-sealinga plurality of segments on the sheet welds the first outer layer to thesecond outer layer at the segment positions.

Again, the process can include forming air escape holes in the sheetproximate the segment positions, and cutting flap slots in thepre-sealed segments.

The step of pre-sealing the plurality of segments comprises contactingthe first outer layer of the sheet with an ultrasonic device having acontacting surface with a plurality of ridges. This can be done byrolling a rotatable anvil of the ultrasonic device on the first outerlayer where the anvil has an undulating ridge pattern on the contactingsurface.

In accord with yet another embodiment of the invention, a blank forforming a reusable plastic corrugated box is provided. The blankcomprises a sheet of plastic corrugated material having a plurality offold lines defining a plurality of side wall panels, a first pluralityof score lines defining bottom flaps extending from a bottom portion ofthe side wall panels, and a first plurality of pre-sealed segments atpositions for slots between the bottom flaps.

The blank can further include a second plurality of score lines. Thesecond plurality of score lines define a plurality of top flapsextending from a top portion of the side wall panels, and a secondplurality of pre-sealed segments at positions for slots between the topflaps.

The blank can further comprise a pre-sealed portion at a first end ofthe sheet and a pre-sealed portion at a second end of the sheet. Thesepre-sealed portions can be used to form a manufacturer's joint.

The blank can be provided with a smooth sealed top edge and a smoothsealed bottom edge. Additionally, the blank can have an air escape holeat each of the first plurality of pre-sealed segments and each of thesecond plurality of pre-sealed segments.

The blank can be further formed to include a cut-out slot in each of thefirst plurality of pre-sealed segments, as well as each of the secondplurality of pre-sealed segments.

The first plurality of pre-sealed segments can have a ridge pattern (orother similar pattern) on an upper surface of the sheet. Similarly, eachof the second plurality of pre-sealed segments can have a ridge patternon an upper surface of the sheet, as well as the pre-sealed portion atthe first end of the sheet. The pre-sealed portion at the second end ofthe sheet can have a ridge pattern on a lower surface of the sheet.

The pre-sealed portion at the first end of the sheet can be formed intoa centrally located glue tab extending outward from the sheet. The gluetab can be connected to the other end of the blank. The corrugatedplastic material has a first thickness and the pre-sealed portion at thefirst end of the sheet and the pre-sealed portion at the second end ofthe sheet collectively have a thickness less than twice the firstthickness. Preferably, the combined thickness is equal to or less thanthe first thickness.

In accordance with another embodiment of the invention, a blank forforming a reusable plastic corrugated box comprises a generallyrectangular sheet of plastic corrugated material having a first outerlayer, a second outer layer and a plurality of flutes extending in afirst direction between the first and second outer layers, a pluralityof fold lines in the first direction defining a first side wall panel, asecond side wall panel, a third side wall panel and a fourth side wallpanel, a first plurality of score lines extending in a second directionperpendicular to the first direction defining a first bottom flapextending from a bottom portion of the first side wall panel, a secondbottom flap extending from a bottom portion of the second side wallpanel, a third bottom flap extending from a bottom portion of the thirdside wall panel and a fourth bottom flap extending from a bottom portionof the fourth side wall panel, and a first plurality of pre-sealedsegments extending between the first and second bottom flaps, the secondand third bottom flaps and the third and fourth bottom flaps. The blankcan further comprise a second plurality of score lines extending in thesecond direction defining a first top flap extending from a top portionof the first side wall panel, a second top flap extending from a topportion of the second side wall panel, a third top flap extending from atop portion of the third side wall panel and a fourth top flap extendingfrom a top portion of the fourth side wall panel, and a second pluralityof pre-sealed segments extending between the first and second top flaps,the second and third top flaps and the third and fourth top flaps.

Additionally, the blank can have a plurality of air escape holes at eachof the first plurality of pre-sealed segments and each of the secondplurality of pre-sealed segments. In a later forming step (which mayremove the portion of the blank having the air escape holes), the blankcan have a cut-out slot in each of the first plurality of pre-sealedsegments and in each of the second plurality of pre-sealed segments.

Each of the first plurality of pre-sealed segments and each of thesecond plurality of pre-sealed segments have a ridge pattern on an uppersurface of the sheet. After the cut-out slots are formed, a portion ofthe ridge pattern can remain around each cut-out slot (i.e., thepre-sealed areas are typically wider than the slot cut-out in thoseareas).

Other aspects of the invention are disclosed in the description, claimsand figures.

BRIEF DESCRIPTION OF THE DRAWINGS

To understand the present invention, it will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a schematic view of the prior art manufacturing process for aplastic corrugated box;

FIG. 2 is a perspective view of an extruded plastic corrugated blank fora plastic corrugated box in accordance with the present invention;

FIG. 3 is a perspective view of a plastic corrugated blank with itsvertical edges sealed in accordance with the present invention;

FIG. 4 is a perspective view of plastic corrugated blank sealed acrossits flutes in accordance with the present invention;

FIG. 5 is a perspective view of a plastic corrugated blank withpre-sealed glue tab and fourth panel areas in accordance with thepresent invention;

FIG. 6 is a perspective view of a plastic corrugated blank withpre-sealed major and minor flap areas in accordance with the presentinvention;

FIG. 7 is a perspective view of a plastic corrugated blank with majorand minor flap scores in accordance with the present invention;

FIG. 8 is a perspective view of a plastic corrugated blank printed withindicia in accordance with the present invention;

FIG. 9 is a perspective view of a plastic corrugated blank after themajor and minor flap areas and glue tab area and fourth panel area havebeen die cut;

FIG. 10 is an enlarged view of the die cut flap area of FIG. 9;

FIG. 11 is a perspective view of a plastic corrugated box constructed inaccordance with the present invention;

FIG. 12 is a schematic view of an apparatus for sealing the edges of theplastic corrugated blank in accordance with the present invention;

FIG. 13 is a perspective view of a manufacturer's joint of a currentblank;

FIG. 14 is a perspective view of a manufacturer's joint in accordancewith the present invention;

FIG. 15 is a perspective view of an apparatus for sealing the edges ofthe plastic corrugated blank in accordance with the present invention;

FIG. 16 is a perspective view of an apparatus for sealing the edges ofthe plastic corrugated blank in accordance with the present invention;

FIG. 17A is a perspective view of a rotary ultrasonic welding apparatusin accordance with the present invention;

FIG. 17B is a plan view of a rotary ultrasonic welding horn and anvilforming a scoreline in a plastic corrugated blank;

FIG. 18 is a perspective view of a rotary ultrasonic anvil in accordancewith the present invention;

FIG. 19 is a plan view of a rotary ultrasonic anvil and horn inaccordance with the present invention;

FIG. 20 is side plan view showing a variety of smooth sealed edgeconfigurations;

FIG. 21 is a perspective view of a corner of a plastic corrugatedcontainer with the edges of the flaps having unsealed open flutes;

FIG. 22 is a perspective view of a corner of a plastic corrugatedcontainer with the edges of the flaps having a sharp die cut seal;

FIG. 23 is a perspective view of a corner of a plastic corrugatedcontainer with the edges of the flaps having a smooth seal;

FIG. 24 is a front plan view of a rotary ultrasonic device anvil havingan undulating, ridged contacting surface for forming a pre-sealed areaon a plastic corrugated blank;

FIG. 25 is a perspective view of the rotary ultrasonic device anvil ofFIG. 24;

FIG. 26 is a perspective view (with an enlarged section) of a blankhaving a plurality of pre-sealed segments formed by the anvil of FIG.24;

FIG. 27 is a perspective view of a blank having a plurality ofpre-sealed segments formed by the anvil of FIG. 24 with a plurality offlap slots cut in the pre-sealed segments.

FIG. 28 is a perspective view of sealing dies forming a smooth sealededge on a corrugated plastic blank;

FIG. 29 is front plan view of one of the sealing dies of FIG. 28;

FIG. 30 is a perspective view of a blank with a plurality of air escapeholes positioned at locations for pre-sealing;

FIG. 31 is a perspective view of a blank with a plurality of escapeholes and a plurality of pre-sealed segments (with an enlarged portion);

FIG. 32 is a perspective view of a stack of corrugated plastic blankshaving a manufacturer's joint that had not been flattened or hadreverted back to original thickness on top of a stack of corrugatedpaper blanks;

FIG. 33A is side plan view illustrating a pre-sealed glue tab and apre-sealed edge area of a fourth panel prior to being connected;

FIG. 33B is side plan view illustrating a pre-sealed glue tab and apre-sealed edge area of a fourth panel after being connected;

FIG. 34 is a perspective view of a stack of corrugated plastic blankswith a manufacturer's joint that does not add thickness to the blank;

FIG. 35 is a perspective view of a plurality of corrugated paper blanksand a plurality of corrugated plastic blanks in a box convertingapparatus;

FIG. 36 is a perspective view of a corner of a plastic corrugatedcontainer with a first sealed portion and a second sealed portion; and,

FIG. 37 is a perspective view of a paper corrugated blank with a “windowframe” of trim material.

DETAILED DESCRIPTION

While this invention is susceptible of embodiments in many differentforms, there is shown in the drawings and will herein be described indetail preferred embodiments of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiments illustrated.

FIG. 1 illustrates a plurality 10 of progressively formed blanks 12 in aknown method of forming plastic corrugated material into boxes usingconventional converting equipment. The method includes the steps ofobtaining a sized plastic corrugated blank 12, printing 14 thereon, ifnecessary, on one or both sides of the plastic corrugated blank 12,sealing the vertical edges 16 and the horizontal edges 18, formingscores (sometimes also referred to as scorelines) 20 therein andcreating side wall panel fold lines 21 therein, and die cutting slots 26for the major flaps 22 and minor flaps 24 (which form the top and bottomof the box) and a glue tab 28 at one end of the blank 12. The steps ofsealing the edges 16, 18 and forming the scores 20 in the plasticcorrugated blank 12 are preferably performed at the same time the blank12 is die cut. Specifically, the edge seals 16, 18 are formed during thedie cutting process using heat and pressure to weld together a firstouter surface 32 and a second outer surface 34 of the plastic corrugatedblank 12. The scores 20 are also formed by applying heat and pressureduring the die cutting. The step of die cutting and forming the scores20 cuts the plastic corrugated blank 12 into the desired shape, formingthe major and minor flaps 22, 24, and the glue tab 28.

The known die cutting involved in this process can include the use ofclam shell or flatbed machines. When using a clam shell die cuttingmachine in current methods, the back of a die board is heated whichtransfers heat to a heating rule. The heated die board cuts and sealsthe plastic corrugated material 12 against a steel plate at ambienttemperature. When using a flatbed die cutting machine, the known methodincludes heating a steel cutting surface to transfer heat through theplastic corrugated material as it moves through the die cutting process.A die board at ambient temperature presses and cuts the plasticcorrugated material 12 against the heated cutting surface to form aheated edge seal.

The step of printing is optional. If printing onto a surface 32, 34 ofthe plastic corrugated blank 12 is desired, it is conventionallyperformed using flexographic, silk screen, digital or other suitablemethods.

The method also includes the steps of assembling a manufacturer's joint(i.e., connecting the glue tab 28 to the other end of the blank 12), andconverting the glued blanks 12 to make finished boxes. In this instance,the boxes would have four side wall panels. The major and minor flapswould be folded to form a top and bottom to the box.

Problems with the known method include variations in quality androbustness of the seal(s) around the edges of the box. In this regard,the heated platen on the die cutter forms a sharp edge on the blank andparticularly along the outer edges of the flaps 22,24, resulting inpotential lacerations to people involved in the process, and in usingthe blanks (an enlarged view of the sharp edges 107 after sealing duringdie cutting is shown in FIG. 22). Moreover, the die cut and scoredblanks cannot be re-used currently with conventional convertingequipment because (in part) the flaps formed in the known method do notreturn to a straight orientation generally coplanar with the side wallpanels of the box after a first use. The known method also results inrelatively slow die cut speeds. Additionally, the known method alsoproduces boxes with a relatively thick manufacturer's joint. Asillustrated in FIG. 32, the relatively thick manufacturer's joint formedin the known method causes a recognizable bowing in the center of astack 240 of the glued plastic corrugated blanks.

The present invention provides a re-useable plastic corrugated box and aprocess for forming plastic corrugated boxes that can be easily cleanedand reused in conventional converting machinery typically used withpaperboard corrugated boxes. The process includes pre-sealing (i.e.,pre-crushing and/or welding or ironing of the corrugated plastic toremove memory) certain areas of a blank (i.e., a rectangular sheet ofcorrugated plastic) to be die cut (such as the flap slot areas and themanufacturer's joint), ultrasonically forming scorelines, and formingsmooth, sealed edges across the flutes of the outer flaps (the smoothededges can be rounded, flat or other configurations). The pre-sealed,ultrasonically scored and smooth, sealed edged sheet can then be placedin conventional converting systems for forming into boxes, and can becleaned and reused in the converting systems. The process describedherein takes into consideration both the movement or flow of plastic andair during the pre-sealing steps.

In accord with an embodiment of the present invention, a plasticcorrugated rectangular blank 100 (FIG. 2) is initially formed usingcurrent plastic corrugated extrusion methods. FIG. 2 shows the blank 100cut to its initial desired size. The size and shape of the blank (andthe container or box formed from the blank) will depend on the desiredapplication for which the finished box will be used. Plastic corrugatedboxes can be used to store and transport any number of products fromfood items to automotive parts and can be made in many sizes and shapes.While the present invention is described in terms of a rectangular boxhaving four side panels connected to top and bottom major and minorflaps, containers and boxes of various sizes and shapes (e.g., square,octagonal, etc.), can be made using the techniques and aspects of theinvention(s) described herein.

When extruded, the blank 100 includes a first outer surface (or skin)102 and a second outer surface 104. Between the first and second outersurfaces 102, 104 are a plurality of generally parallel flutes 106.Flutes formed in a profile board style corrugated plastic sheet arecreated by ribs between the two outer sheets 102, 104 (as opposed toundulating waves of material commonly found in paper corrugation andother types of corrugated plastic). As illustrated in FIG. 2, the blank100 includes top and bottom edges 108 and 110 and first and second sideedges 112 and 114. Terms such as “top,” “bottom,” “side” etc., are madewith respect to the orientation of the blank, box or other components asshown and positioned in the Figures to facilitate the descriptionthereof. Such terms are not intended to limit the invention in anymanner and may change from Figure to Figure. For example, the “top” edge108 shown in one Figure may end up being the edge of the “bottom” flapsas shown in another Figure. The top and bottom edges 108 and 110 runacross the flutes 106 and will form the outer edges of any flaps formedin the blank 112 (or the top edge of the side panels of a half slottedcontainer—HSC).

In one embodiment, the blank 100 is sealed along the first and secondside edges 112 and 114 in the direction of the flutes 106, creating afirst side edge seal 118 and a second side edge seal 116 (as describedbelow, this can instead be preferably accomplished when pre-sealing anentire strip on either end of the blank 100 to form a manufacturer'sjoint and pre-sealing areas for slots between top and bottom flaps).FIG. 3 shows the second side edge seal 116 in an enlarged portion alongthe second side edge 114. It will be understood that the similar firstside edge seal 118 will be created at the first side edge 112. The blank100 is placed on a conveyor 206 (See FIGS. 15 and 16), where a hot airblower 207 (or multiple blowers) heats the first and second side edges112 and 114 of the blank 100. A knife cuts through the flutes 106 on theedge to be sealed. The blank 100 is moved through multiple heated dies208 to form a smooth edge. The blank 100 is then moved through anidentically shaped cooling die 210. The heating and cooling dies 208 and210 have generally C-shaped cross-sections 204. The sealing of both sideedges 112, 114 can also be performed in a single pass. It is recognizedthat the die or dies can be progressive, meaning instead of a singledie, there are multiple dies having a progressively different shapeleading up to a final die with the final desired shape formed therein.

The heated dies 208 include a heated sealing and forming die 202 with agenerally C-shaped section 204. The heated sealing and forming die 202contacts the edges 112 and 114, and partially melts or reforms the edgeto seal it and create a smooth rounded edge surface.

The top and bottom edges 108, 110 are then sealed as illustrated in FIG.28. FIG. 28 shows a first sealing die 220 contacting the bottom edge 110and a second sealing die 222 contacting the top edge 108 as the blank100 is moved past the dies 220, 222. As shown in FIG. 29, the dies 220,222 have an open slot 224 for receiving the edge portion of the blank100. A heated element, such as that shown in cross-section in FIG. 12contacts the edges of the blank 100 to form a smooth sealed edge as theblank 100 moves past the dies 220, 222 (in the direction of the arrow226). The open slot 224 of each die 220, 222 can further include aflared portion 228 for receiving the leading portion of the blank 100 asit approaches the dies 220, 222.

As evident in FIG. 28, prior to entering the dies 220, 222, the edge ofthe blank 100 has open sides and exposed flutes 106. After passingthrough the dies 220, 222, a smooth sealed edge (e.g., 122) is formedand the interior of the blank as well as the flutes are not exposed.

FIG. 4 shows the top and bottom edges 108 and 110 sealed using the dies220, 222 creating top and bottom smooth edge seals 120 and 122,respectively. Top and bottom edge seals 120 and 122 are sealed acrossthe flutes 106, thereby closing the openings into the flutes which willprevent debris, liquids or other contaminants from becoming trapped inthe interior of the sheet between the flutes 106. Moreover, this smoothsealing provides safe, smooth rounded seals 120 and 122 on the edges ofthe blank 100 most frequently contacted by human hands, namely the topedge 108 and bottom edges 110. It will be understood that this sealingprocess can be performed at any desired point in the process of thepresent invention. Additionally, the sealed edges can be flat or othershapes so long as they are relatively smooth. FIG. 20 shows (incross-section) a rounded smooth sealed edge 120 and a number of possiblevariations 230, 232, 234 of smooth sealed edges.

As illustrated in FIG. 5, after sealing of the top and bottom edges 108,110 (i.e., across the open or exposed flutes 106), the blank 100 ispre-sealed proximate the first and second side edges 112 and 114 in thedesired area 124 for a glue tab 126 (the glue tab 126 is shown in FIG.9) and a desired connection area 128 of a fourth side panel 130 (i.e.the glue tab 126 is considered to extend from the first side wall panel125 of the completed box and is connected to the other end of the boxdesignated as the fourth side wall panel 130—see e.g., FIG. 10). Asmentioned above, this pre-sealing step can also seal the side edges 112,114 of the blank 100 and thus the separate side edge sealing stepdiscussed above may be eliminated. Moreover, the side edge pre-sealingcan be done at the same time as pre-sealing the slot areas 132 (i.e.,the areas between the flaps) as shown in FIG. 6 and discussed below. Thepre-sealing can be accomplished using any suitable means, including heatand compression, plunge ultrasonic welding, or rotary ultrasonicwelding.

In a subsequent step shown in FIG. 9, the pre-sealed edge 124 is cutleaving a centrally located glue tab 126. The glue tab 126 is connected(e.g., glued, although ultrasonic welding or other means may be used) tothe pre-sealed area 128 of the fourth side wall panel 130 to create aplastic corrugated box. The glue tab 126 and area of the fourth sidewall panel 128 the glue tab 126 is ultimately connected to is referredto as the “manufacturer's joint.” An object of the invention is tocreate a manufacturer's joint that will not cause a stack of unformedboxes to unreasonably bow out in that area. For example, FIG. 32 whichshows a stack 240 of corrugated plastic blanks formed using prior knownconverting processes on top of a stack 242 of paper blanks. As evidentin this Figure, the stack 240 of corrugated plastic blanks has a thickermiddle section due to the manufacturer's joint. Instead, it is desirableto reduce any bowing and have a relatively flat stack 244 of unformedboxes as shown in FIG. 34. Accordingly, it is desirable that at leastone (and preferably both) of the glue tab 126 and the fourth panel area128 be flattened during pre-sealing to a thickness less than the blankthickness (i.e., if one or both are pre-sealed to less than the blankthickness, the total thickness in that area will be less than two blankthicknesses). Moreover, it is preferable that the manufacturer's jointwill have no added thickness beyond the thickness of the blank. That is,it is preferred that the glue tab 126 and fourth panel area 128 arepre-sealed so that the combined total thickness of the glue tab 124 andfourth panel area 128 is preferably equal to or less than a single blankthickness as shown in FIGS. 33A and B.

As illustrated in FIG. 14, a pre-sealed, pre-sealed glue tab 126 isconnected to a pre-sealed, pre-sealed area 128 of the fourth side wallpanel 130. This results in a manufacturer's joint having zero increasedthickness 150. In comparison, a box 154 formed using current methods hasan increased thickness 152 (an additional blank thickness) at themanufacturer's joint as shown in FIG. 13.

The blank 100 is also pre-sealed in the desired areas to form flattenedand sealed segments 132 from which major and minor flap slots 142 of aresulting finished box 136 will be die cut (see FIGS. 6-10). Thepre-sealing flattens the blank 100 in the desired slot areas,effectively welding the inner and outer surfaces 102, 104 and flutes 106to each other. The pre-sealing can be created by any suitable means,including plunger ultrasonic welding, rotary ultrasonic welding or byusing heat and compression rollers, with a preferred method being rotaryultrasonic welding.

As shown in FIG. 7, score lines 138 are formed in the blank 100. Thescore lines 138 will form the major and minor flaps 146, 148 of thefinished box 136. The scoring operation can be performed in accord withthat disclosed in co-pending U.S. Ser. No. 13/273,019, Attorney DocketNo. 52045-7426, filed Oct. 13, 2011, now U.S. Pat. No. 8,864,017, thecontents of which are incorporated herein by reference. Briefly, thescoring from such application provides an intermittent welded score,leaving some portions of the score lines unwelded (i.e., not welded).Scoring using this method allows the major and minor flaps to be easilyclosed yet retain enough “memory” or “spring-back” such that afterfolding the flaps at the score, the flaps will return to its originalshape and can be reused (after cleaning) in box converting machinery. Itwill be understood that the pre-sealing and the scoring can be performedsuch that the scoring takes place before the pre-sealing.

In another embodiment, the score lines 138 are formed using ultrasonicdevices, such as with a rotary ultrasonic device, to reshape thecorrugated plastic along the score line. The score lines using rotaryultrasonic reshaping can be a continuous line, or can be segmented, withsections of the score line left unchanged. Using rotary ultrasonicreshaping to form the score lines 138 allows easy folding of the majorand minor flaps 146, 148 while having enough memory to return the flapsto a straight position after use (i.e., having the flaps align with thesides of the box as shown in the stack 244 of FIG. 34).

The rotary ultrasonic reshaping step of the present invention includesthe plastic corrugated blank 100 being run in an ultrasonic device 300illustrated in FIG. 17A. The ultrasonic device 300 includes an anvil 302and a horn 304 (see e.g., FIGS. 17-19). The horn 304 imparts ultrasonicenergy into the blank 100, thereby enabling the anvil to form a shapedscore into the material. In extreme instances, the device 300 can weldthe inner and outer sheets 102 and 104. Alternatively, the anvil 302 canimpart the ultrasonic energy to the blank 100. Both the horn 304 and theanvil 302 can rotate about an axis.

The anvil 302 is shown having a central raised portion or projection 310along a contacting surface of the anvil. The raised portion 310 is usedto form the score lines 138. In effect, the plastic in the blank 100reshapes around the projection 310 during the scoring operation to havea generally V-shaped cross-sectional profile as illustrated in FIG. 17B.It has been found that an angle 308 on the raised center portion 310 ofthe anvil 302 in the range of 90° to 120°, with a preferred angle 308 ofabout 110°, will provide the desired score lines 138 using rotaryultrasonic reshaping.

It has also been found that for the step of creating score lines 138using rotary ultrasonic reshaping, a frequency in the range of 20kilohertz is preferred. For creating the pre-sealed areas 124, 128 or132 (when using ultrasonic devices) for the glue tab 126, fourth sidewall panel area 128 and the major and minor flap slots 142, frequenciesin the range of 15, 20, or 40 kilohertz are suitable.

The blank 100 can be printed upon if desired as shown in FIGS. 8 and 9.Printing can be done at any convenient step in the process. Printing canbe done with silk screen, flexographic, digital, or any other suitableprinting process. Printed indicia 140 on the blank 100 can includeproduct information for products stored in the box, Department ofTransportation required information, bar coding, or any other desiredindicia.

After pre-sealing, the blank 100 can be die cut on any conventionalcorrugated die cut equipment, including quick set, clam shell, rotary orflatbed die cutting machines. The blank 100 is die cut in the areashaving flattened segments 132 that have been pre-sealed where the majorand minor flap slots 142 are desired (see FIGS. 9 and 10). The slots 142are cut in the direction of the flutes 106. The slots 142 separate theflaps 146, 148 from each other. As shown in FIG. 10, the die cut slots142 are narrower than the pre-sealed areas 132, leaving a sealed edge144 around each slot 142. The pre-sealing of the slot areas 132 resultsin a sealed edge 144 that is more consistent than those formed in diecutting without pre-sealing. The die cut process also forms the glue tab126. Alternatively, the major and minor flap slots 142 may also be cutor formed during the crushing and sealing operation described above. Thedie cut process also forms fold lines 123 separating the middle sectionof the blank 100 into the four side panels 125, 127, 129, and 130.

After being die cut, the blank 100 is folded so that the glue tab 126 isbonded to the edge area 128 of the fourth side wall panel 130, and themajor and minor flaps 146, 148 are aligned or coplanar with therespective side wall panels 125, 127, 129, 130. A stack 244 of suchglued blanks 100 is shown in FIG. 34.

The stack 244 is placed into a box converter to make a completed box. Apartially completed box 136 is shown in FIG. 11. After opening the box136 as shown in FIG. 11, the flaps are later folded to form a bottom andtop of the box (the top flaps are typically folded after loading the boxwith the product being packaged). As set forth above, the presentinvention can also be used to form half slotted containers (i.e., opentop boxes having only bottom flaps) as well as other types of boxeshaving different shapes.

FIGS. 21-23 provide a comparison of the outer edges of prior boxes withthe current invention. FIG. 21 shows a first flap and a second flap of abox with edges that have not been sealed. Instead, the flaps have openedges showing the openings formed between the flutes 106. Open edgesallow debris and liquid to enter the flutes 106 and contaminate the boxfor further use. Moreover, it would be difficult, if not impossible, toclean such boxes (especially using any automated process). FIG. 22 showsa first flap and a second flap having edges 107 that were sealed usingheat and pressure to weld the edges together. This is typicallyaccomplished during a die cut process. These edges are sharp, requiringthose handling the boxes to wear gloves and other protective clothing.FIG. 23 shows a first flap and a second flap having a smooth roundedseal 120 in accordance with an aspect of the present invention. Whilethe edge 120 of FIG. 23 is shown as being rounded, it can be flat oranother shape (such as those shown in FIG. 20) as long as the box issealed to a smooth edge at the typical human contact points.Additionally, the slot area between the flaps had been pre-sealed asdiscussed above, and has a smoother edge than the slot area of the diecut sealed box shown in FIG. 22.

FIG. 17B illustrates forming the scoreline 138 in the blank 100 usingthe ultrasonic horn 304 and anvil 302. As shown in cross-section, theprojection 310 on the anvil 302 forms a V-shaped section into the bottomof the blank 100. It has been found that by manipulating certainvariables associated with this process (e.g., the gap between the anvil302 and the horn 304, the speed of the blank with respect to the anvil302 and horn 304, the frequency or energy of the ultrasound, and theprofile of the projection) that the resulting scoreline can be as strongor weak as desired for a particular use. For example, to create ascoreline with no or little memory (i.e., to form a limp flap), decreasethe gap and speed of the blank and increase the frequency of theultrasound. In contrast, to form a scoreline having a lot of memory (orspring-back), increase the gap and speed, and decrease the frequency. Amultitude of variations in the flap memory or lack thereof are possibleby gradually increasing or decreasing some or all of these variables.

The present invention is designed to handle various problems that may beencountered during some of the pre-sealing operations that can result information of an unacceptable box. For example, excess molten plastic maybe formed during a pre-sealing operation. To accommodate this, thepresent invention provides a mechanism for managing the molten plastic,and directing it where to go. Additionally, the pre-sealing operationcan encounter problems due to trapped air (i.e., between the ribs in theflutes) which can form bubbles and blowout holes as the pre-sealed areasare flattened. To fix this problem, air escape holes can be provided inthe blank prior to the pre-sealing operation.

To direct molten plastic, the present invention contemplates contactingthe areas to be pre-sealed with a surface having some shape (e.g., peaksand valleys) that directs the molten plastic to particular areas. Forpre-sealing using a rotary ultrasonic device, this can be accomplishedby providing a ridged pattern on one or both of a rotary anvil and horn.

FIGS. 24 and 25 show a rotary ultrasonic anvil 250 in the form of aroller for use in pre-sealing portions of a corrugated plastic blank 252(the blank 252 is shown in FIGS. 26-27). The anvil 250 includes an outercontacting surface 254 having an undulating, ridged pattern. The anvil250 is utilized to contact the top or bottom surface of the blank 252(depending on the area being pre-sealed) during a pre-sealing operation(in contrast, a smooth anvil and horn were utilized for the embodimentof FIGS. 2-10). The anvil 250 cooperatively works with a rotaryultrasonic horn (identical or similar to the horn 304 used for formingthe scorelines 138), which is also in the shape of a roller. The horntypically has a smooth outer surface (although in some embodiments, boththe horn and the anvil can include a contacting surface having somestructure or pattern). The horn is aligned or registered with the anvil250 and contacts an opposing side of the blank 254. Again, while thehorn typically provides the ultrasonic energy, either of the horn oranvil 250 can be configured to provide the necessary ultrasonic energyto accomplish the task. As shown, the contacting surface 254 of theanvil 250 has slightly rounded corners 256. This eliminates a sharp edgethat could damage the plastic corrugated material during pre-sealing.

The horn and anvil 250 contact the blank 252 on the ends 258, 260 of theblank 252 for (later) formation of a glue tab and pre-sealed fourth sidepanel area, and at the slot locations to form pre-sealed segments 262.The horn and anvil 252 are each mounted on a camming mechanism whichseparates and brings them together at the proper locations on the blank252 (more than one horn/anvil combination can be used in the formingapparatus).

As illustrated in FIG. 26, the pre-sealed areas 258 and 262 are shownhaving an undulating ridged pattern from contacting the anvil 252 (thehorn and anvil 250 are reversed for pre-sealing the end 260—thus thelower surface will have the undulating ridged pattern in that area). Theexcess molten plastic formed from pre-sealing the corrugated plastic isdirected by the pattern 254 on the anvil 250 and forms the ridges of thepattern on the surface of the blank 252. As shown in FIG. 27, a portionof this pattern may remain after cutting the slots 264 and glue tab 266.

FIGS. 30 and 31 illustrate use of an air escape hole during theformation process. A plurality of V-shaped cut outs 268 are made to thesmooth sealed edges of the blank 100 at locations that are to bepre-sealed as shown in FIG. 30. These cut-outs are also called“bird-bites” because of their V-shape. Making these cut outs 268 in thesealed edge allows air in the pre-sealed areas (e.g., 132) an escapepath when the area is being crushed or flattened. Each cut out 268 goesall the way through the flutes that are being crushed. A flattenedV-shaped cut 268 remains after the pre-sealing operation as shown inFIG. 31. While the cut outs 268 are shown as V-shaped, other shapes(e.g., an arcuate shape) can be used.

The cut outs 268 also help provide a place for molten plastic to go (inaddition to or possibly in place of the ridged ultrasonic devicedescribed above) during the pre-sealing process. Without the cut outs268, molten plastic will often squeeze out and migrate past the plane ofthe smooth edge seal during the crushing process. The cut out 268 ispositioned in the area of the pre-seal 132 that is later cut away toform the slot 142. Accordingly, it does not appear in the completed box.

While FIGS. 30 and 31 show the pre-sealed area 132 having a smooth uppersurface, these areas can also be formed using the ridged anvil 250 asdiscussed above. In this embodiment, the upper surface will have theundulating ridges (or other pattern) shown in FIG. 24, along with theV-shaped cut out 268.

In a typical pre-sealing operation, the blank 100 or 252 has a thicknessof 0.140 inches. To form the pre-sealed areas the horn and anvil arespaced a distance of 0.013 inches apart. After the pre-sealed areas passthrough the horn and anvil, they are flattened to a thickness of 0.052inches.

In accordance with another embodiment, only a minimal amount of sealingis done in the slot area. Because the slot is cut in the direction ofthe flutes 106, an existing natural barrier is provided along the sidesof the slot. That is, the adjacent flute, or next flute over, provides awall along the length of the slot that prevents contaminants fromcollecting or entering the area between the outer sheets of thecorrugated plastic material. The only areas that require sealing are thevery end of the slot (which will have open flutes) and (possibly) thetop of the slot near the smooth sealed edge. FIG. 36 shows a flap slotthat has a small sealed portion 270 at the end of the slot, and smallsealed portions 272 on the corner of each flap defining the top of theslot. The bottom and top sealed portions 270, 272 can be sealed usingheat and pressure or ultrasonic sealing. This approach is possibly lowerin capital investment than the other approaches discussed herein.

FIG. 35 shows a plurality of plastic corrugated blanks 274 (formed inaccordance with the present invention) in a box converting apparatus276. The plastic corrugated blanks 274 are intermingled with papercorrugated blanks 278.

Prior to the present invention, when die cutting paper or plasticcorrugated boxes, the conventional process used a blank that is slightlylarger than the (eventual) die cut box. The die cut process would cutout the entire perimeter of the box (and all cut out portions), leavinga “window frame” of trim material 280 around the perimeter as shown inFIG. 37. When die cutting using rotary or flatbed die cut equipment, thewindow frame 280 is used to pull the blanks through the equipment and isthen stripped away. In the present invention, the top and bottom edgesof the blank are not cut away and instead are provided a smooth seal.Thus, the present process does not have the wasted “window frame”material.

While the term “horn” is typically used to describe the part of thesystem that emits the ultrasonic energy, it is understood that in any ofthe embodiments that ultrasonically reshape and/or weld the corrugatedplastic material, either the horn or the anvil can emit the ultrasonicenergy.

While the specific embodiments have been illustrated and described,numerous modifications come to mind without significantly departing fromthe spirit of the invention, and the scope of protection is only limitedby the scope of the accompanying Claims.

1. A plastic corrugated box comprising: a wall panel having a bottomportion; and, a flap connected to the bottom portion of the wall panelby an ultrasonically formed score line.
 2. The plastic corrugated box ofclaim 1 wherein the wall panel includes a smooth sealed upper edge. 3.The plastic corrugated box of claim 1 wherein the flap includes a smoothsealed lower edge.
 4. The plastic corrugated box of claim 1 wherein: thewall is a first side wall and the flap is a first bottom flap andfurther comprising: a second side wall panel having a top portion and abottom portion connected to the first side wall panel by a first foldline; a third side wall panel having a top portion and a bottom portionconnected to the second side wall panel by a second fold line; and, afourth side wall panel having a top portion and a bottom portionconnected to the third side wall panel by a third fold line and to thefirst side wall panel.
 5. The plastic corrugated box of claim 4 furtherwherein the flap is a first bottom flap and further comprising: a secondbottom flap connected to the bottom portion of the second side wallpanel by a second ultrasonically formed score line; a third bottom flapconnected to the bottom portion of the third side wall panel by a thirdultrasonically formed score line; and, a fourth bottom flap connected tothe bottom portion of the fourth side wall panel by a fourthultrasonically formed score line.
 6. The plastic corrugated box of claim5 wherein the first side wall panel includes a smooth sealed upper edge,the second side wall panel includes a smooth sealed upper edge, thethird side wall panel includes a smooth sealed upper edge, and thefourth side wall panel includes a smooth sealed upper edge.
 7. Theplastic corrugated box of claim 6 wherein the first bottom flap includesa smooth sealed lower edge, the second bottom flap includes a smoothsealed lower edge, the third bottom flap includes a smooth sealed loweredge, and the fourth bottom flap includes a smooth sealed lower edge. 8.The plastic corrugated box of claim 5 further comprising a first topflap connected to the top portion of the first side wall panel by afifth ultrasonically formed score line.
 9. The plastic corrugated box ofclaim 8 further comprising: a second top flap connected to the topportion of the second side wall panel by a sixth ultrasonically formedscore line; a third top flap connected to the top portion of the thirdside wall panel by a seventh ultrasonically formed score line; and, afourth top flap connected to the top portion of the fourth side wallpanel by an eighth ultrasonically formed score line.
 10. The plasticcorrugated box of claim 1 wherein the first top flap has a smooth sealedupper edge.
 11. The plastic corrugated box of claim 9 wherein the firsttop flap has a smooth sealed upper edge, the second top flap has asmooth sealed upper edge, the third top flap has a smooth sealed upperedge, and the fourth top flap has a smooth sealed upper edge.
 12. Theplastic corrugated box of claim 1 wherein the score line allows foldingof the bottom flap with respect to the wall panel and has sufficientmemory to return the bottom flap into alignment with the wall panelafter being folded.
 13. The plastic corrugated box of claim 5 whereinthe first score line allows folding of the first bottom flap withrespect to the first side wall panel and has sufficient memory to returnthe first bottom flap into alignment with the first side wall panelafter being folded, the second score line allows folding of the secondbottom flap with respect to the second side wall panel and hassufficient memory to return the second bottom flap into alignment withthe second side wall panel after being folded, the third score lineallows folding of the third bottom flap with respect to the third sidewall panel and has sufficient memory to return the third bottom flapinto alignment with the third side wall panel after being folded, andthe fourth score line allows folding of the fourth bottom flap withrespect to the fourth side wall panel and has sufficient memory toreturn the fourth bottom flap into alignment with the fourth side wallpanel after being folded.
 14. The plastic corrugated box of claim 8wherein the fifth score line allows folding of the first top flap withrespect to the first side wall panel and has sufficient memory to returnthe first top flap into alignment with the first side wall panel afterbeing folded.
 15. The plastic corrugated box of claim 14 wherein thesixth score line allows folding of the second top flap with respect tothe second side wall panel and has sufficient memory to return thesecond top flap into alignment with the second side wall panel afterbeing folded, the seventh score line allows folding of the third topflap with respect to the third side wall panel and has sufficient memoryto return the third top flap into alignment with the third side wallpanel after being folded, and the eighth score line allows folding ofthe fourth top flap with respect to the fourth side wall panel and hassufficient memory to return the fourth top flap into alignment with thefourth side wall panel after being folded.
 16. The plastic corrugatedbox of claim 1 wherein the ultrasonically formed score line does notextend across a full width of the flap and the wall panel.
 17. Theplastic corrugated box of claim 1 wherein the ultrasonically formedscore line comprises a plurality of spaced apart ultrasonically formedsegments across a width of the flap and wall panel.
 18. A plasticcorrugated blank for forming a box comprising: a generally rectangularportion of plastic corrugated material having a plurality of fold linesforming side edges of a plurality of side wall panels, the plasticcorrugated material having a plurality of ultrasonically formed scorelines, each score line forming an edge between one of the plurality ofside wall panels and a flap connected to the one side wall panel. 19.The plastic corrugated blank of claim 18 wherein the plurality of scorelines are a first plurality of score lines and further including asecond plurality of ultrasonically formed score lines, each score lineof the second plurality of ultrasonically formed score lines forming anedge between one of the plurality of side wall panels and a top flapconnected to the one side wall panel.
 20. The plastic corrugated blankof claim 19 wherein the blank has a smooth sealed top edge and a smoothsealed bottom edge. 21-80. (canceled)